Hormones
Hormones are chemicals that are responsible for functions of the body and brain. A hormone called cortisol is a stress hormone that prepares the body for threats and danger. During a dangerous situation, the release of cortisol leads to the response of the person to fight or to flee, and in the process, decreases appetite. When cortisol levels are higher than normal for a long time, depression and loss of appetite are common. Stress hormones such as cortisol are often excessive in people with bulimia and anorexia. A hormone known as leptin tells the hypothalamus to send out signals of hunger or fullness. Leptin has shown to be defective in anorexics, bulimics, binge-eaters, and people who are obese. People with reduced leptin may not know what it feels like to be hungry or full.
Genetics
Some scientists think that eating disorders are inhereted, and caused by genetics. James I. Hudson conducted a study of obese people with and without the binge eating disorder. He found that binge eating disorder is twice as common in family members of binge-eaters as it is in people who do not have the disorder. This proves that binge eating may be a genetic disorder. The same goes for anorexia. One study indicates that an individual is eight times more likely to be anorexic if they are related to someone with the disorder. Studies on twins show that bulimia may also run in families. Little is known about which genes are linked to eating disorders, but research has proven that these diseases are likely to be genetic.